Techniques for Aerodynamic Analysis of Cornering Vehicles

Abstract

When a vehicle travels through a corner it can experience a significant change in aerodynamic performance due to the curved path of its motion. The yaw angle of the flow will vary along its length and the relative velocity of the flow will increase with distance from the central axis of its rotation. Aerodynamic analysis of vehicles in the cornering condition is an important design parameter, particularly in motorsport. Most racing-cars are designed to produce downforce that will compromise straight-line speed to allow large gains to be made in the corners. Despite the cornering condition being important, aerodynamicists are restricted in their ability to replicate the condition experimentally. Whirling arms, rotary rigs, curved test sections and bent wind tunnel models are experimental techniques capable of replicating some aspects of the cornering condition, but are all compromised solutions. Numerical simulation is not limited in the same way and permits investigation into the condition. However, cornering introduces significant change to the flowfield and this must be accommodated for in several ways. Boundary conditions are required to be adapted to allow for the curved flow occurring within a non-inertial reference frame. In addition, drag begins to act in a curved path and variation in Re occurs within the domain. Results highlight the importance of using correct analysis techniques when evaluating aerodynamic performance for cornering vehicles. Figure 1. The steady-state cornering flow conditions.

The Effect of Cornering on the Aerodynamics of a Multi-Element Wing in Ground Effect

“…Thus, it was aligned to the tangent of the body's path whilst the side-force, by definition, as the force acting orthogonally to the drag force; as illustrated in Figure 11. This follows Keogh et al [20] and Keogh [22], that the drag force is linearly proportional to the moment acting about the GCoR (M DWi ) to oppose the circular path of the body. The lift force vector is unaltered.…”

“…The cornering condition requires the consideration of both the topology of the computational domain and the simulation of motion. Regarding the topology, either a rectangular computational domain or a curved domain must be selected with the associated boundary conditions, as discussed in [20]. Whilst it is easier to apply the appropriate boundary conditions with a curved domain, it does not allow the simulation of multiple corner radii via the same domain or mesh nor does it allow the simulation of multiple operating conditions such as the straight-line condition.…”

Numerical Analysis of Aerodynamic Impact on Passenger Vehicles during Cornering

“…Since the vehicles velocity vector is not constant over the entire body while cornering, the drag force calculation needs to be modified. The drag force is calculated as [4]…”

“…Fuel consumption is measured with standardized driving cycles such as Worldwide harmonized Light vehicles Test Procedures (WLTP) [2]. The WLTP cycle only considers flows in the driving direction of the vehicle, however, studies in simplified geometries have shown that aerodynamic properties can be a ected by cornering [3], [4]. Keogh [3], for instance, studied the impact of cornering on an inverted wing and found significant changes in the flow structures.…”

“…This is a major simplification that does not capture the essence of cornering, a curvature of the freestream flow. Another approach is to use a curved test section [4], however, this also fails to reproduce the flow conditions as in actual cornering as it gives rise to pressure gradients between the walls. There are other aggravating factors with physical tests due to the dynamics that arise when cornering, such as roll, body slip and steering angles with rotating wheels.…”